This invention relates generally to copier apparatus, and, more particularly, to a roll fusing system for fixing electroscopic toner material to a support member.
In the process of xerography, a light image of an original to be copied is typically recorded in the form of a latent electrostatic image upon a photosensitive member with subsequent rendering of the latent image visible by the application of electroscopic marking particles, commonly referred to as toner. The visual image can be either fixed directly upon the photosensitive member or transferred from the member to a sheet of plain paper with subsequent affixing of the image thereto.
There are various ways of fusing or affixing the toner particles to the support member, one of which is by the employment of heat. In order to permanently affix or fuse electroscopic toner material onto a support member by heat, it is necessary to elevate the temperature of the toner material to a point at which the constituents of the toner material coalesce and become tacky. This action causes the toner to be absorbed to some extent into the fibers of the support member which, in many instances, constitute plain paper. Thereafter, as the toner material cools, solidification of the toner material occurs causing the toner material to be firmly bonded to the support member. In both the xerographic as well as the electrographic recording arts, the use of thermo energy for fixing toner images onto a support member is old and well known.
One approach to thermofusing of electroscopic toner images onto a support has been to pass the support with the toner images thereon between a pair of opposed roller members, at least one of which is either externally or internally heated. During operation of a fusing system of this type, the support member to which the toner images are electrostatically adhered is moved through the nip formed between the rolls with the toner images contacting the fuser roll to thereby effect heating of the toner images within the nip. The backup roll of the fuser roll pair is usually constructed so that the fuser roll creates a depression in the backup roll resulting from the bias force which forces the rolls into engagement. Such depression forms an elongated nip which extends the contact time of the toner images with the heated fuser roll structure.
During periods when the copier is not being utilized it is necessary to provide means for preventing the rolls from remaining in engagement. If the foregoing is not provided, the softer backup roll would become flattened in the area of engagement with the fuser roll thereby resulting in problems of proper fusing and paper handling.
One approach to preventing the flattening of the backup roll has been to provide mechanism which effects disengagement of the rolls during inoperative periods of the machine. It will be appreciated that the drive mechanism for imparting rotation to the rolls must accommodate such disengagement with subsequent engagement.
Heretofore, such mechanisms have been very complex and thus quite a bit more expensive both from the standpoint of manufacture and from the standpoint of maintenance during the life of the copying apparatus.
Accordingly, the principal object of this invention is to provide a new and improved copying apparatus.
It is a more particular object of this invention to provide a new and improved roll fusing apparatus for utilization in an electrostatic copier apparatus. Another object of this invention is to provide a roll fusing apparatus which utilizes substantially fewer components than known roll fuser apparatus and which is therefore less costly to manufacture as well as maintain.
Yet another object of this invention is to provide new and improved drive means for a roll fusing apparatus.